"Evidence for decreased androgen 5 alpha-reduction in skin and liver of men with severe acne after 13-cis-retinoic acid treatment." - Boudou 1994, describes a decrease in the mean androsterone/etiocholanolone ratio from 1.70 (SD = 0.35) pre-treatment, to 1.10 (SD = 0.10) post-treatment, indicative of a "metabolic deviation from the 5-alpha to 5-beta-reduction pathway in the liver"